Share This

This illustration depicts the use of a technique developed at Purdue to identify bacteria in its ambient environment using mass spectrometry. The technique, called desorption electrospray ionization, or DESI, could be used to create a new class of fast, accurate detectors for applications ranging from food safety to homeland security.

Credit: Purdue University, Department of Chemistry

Researchers at Purdue University have used a new technique to rapidly detect and precisely identify bacteria, including dangerous E. coli, without time-consuming treatments usually required.

Related Articles

The technique, called desorption electrospray ionization, or DESI, could be used to create a new class of fast, accurate detectors for applications ranging from food safety to homeland security, said R. Graham Cooks, the Henry Bohn Hass Distinguished Professor of Chemistry in Purdue's College of Science.

Using a mass spectrometer to analyze bacteria and other microorganisms ordinarily takes several hours and requires that samples be specially treated and prepared in a lengthy series of steps. DESI eliminates the pretreatment steps, enabling researchers to take "fingerprints" of bacteria in less than a minute using a mass spectrometer.

"This is the first time we've been able to chemically analyze and accurately identify the type of bacteria using a mass spectrometer without any prior pretreatment within a matter of seconds," Cooks said.

New findings show how the Purdue researchers used the method to detect living, untreated bacteria, including E. coli and Salmonella typhimurium, both of which cause potentially fatal infections in humans.

"There is always an advantage to the analysis of living systems because the bacteria retain their original properties," Cooks said.

The findings are detailed in a paper appearing Jan. 7 in the journal Chemical Communications. The paper was written by chemistry graduate students Yishu Song, Nari Talaty and Zhengzheng Pan; Andy W. Tao, an assistant professor of biochemistry; and Cooks.

Mass spectrometry works by turning molecules into ions, or electrically charged versions of themselves, inside the instrument's vacuum chamber. Once ionized, the molecules can be more easily manipulated, detected and analyzed based on their masses. The key DESI innovation is performing the ionization step in the air or directly on surfaces outside of the mass spectrometer's vacuum chamber. When combined with portable mass spectrometers also under development at Purdue, DESI promises to provide a new class of compact detectors.

Purdue researchers are focusing on three potential applications for detecting and identifying pathogens: food safety, medical analysis and homeland security. Such a detector could quickly analyze foods, medical cultures and the air in hospitals, subway stations and airports, Cooks said.

The researchers are able to detect one nanogram, or a billionth of a gram, of a particular bacterium. More importantly, the method enables researchers to identify a particular bacterium down to its subspecies, a level of accuracy needed to detect and track infectious pathogens. The identifications are based on specific chemical compounds, called lipids and fatty acids, in the bacteria.

"We can determine the subspecies and glean other information by looking at the pattern of chemicals making up the pathogen, a sort of fingerprint revealed by mass spectrometry," Cooks said. "Conventional wisdom says quick methods such as ours will not be highly chemically or biologically specific, but we have proven that this technique is extremely accurate."

The procedure involves spraying water in the presence of an electric field, causing water molecules to become positively charged "hydronium ions," which contain an extra proton. When the positively charged droplets come into contact with the sample being tested, the hydronium ions transfer their extra proton to molecules in the sample, turning them into ions. The ionized molecules are then vacuumed from the surface into the mass spectrometer, where the masses of the ions are measured and the material analyzed.

Such a system could alert employees in the food and health-care industries to the presence of pathogens and could provide security personnel with a new tool for screening suspicious suitcases or packages.

Song will further the research, conducting experiments to look for bacterial contaminants in foods. Ongoing work by Talaty with international E. coli expert Barry Wanner, a professor in Purdue's Department of Biological Sciences, will apply the method to living bacteria in so-called biofilms.

DESI has been commercialized by Indianapolis-based Prosolia Inc.

"This method could be applied very soon because the hardware is already available," Cooks said.

The DESI instrument and mass spectrometer used in the research are housed at the Bindley Bioscience Center at Purdue's Discovery Park.

Cooks also is leading work to build miniature versions of the normally bulky mass spectrometer, creating shoebox-size instruments that weigh about 10 kilograms (22 pounds), compared to about 30 times that weight for a conventional mass spectrometer.

Much of the research funding was provided by the National Science Foundation, the Office of Naval Research and by Prosolia through the Indiana 21st Century Research and Technology Fund.

More From ScienceDaily

More Plants & Animals News

Featured Research

Mar. 31, 2015 — Researchers have recorded the first direct observations of the micro-scale mechanisms behind the ability of skin to resist tearing. The results could be applied to the improvement of artificial skin, ... full story

Mar. 31, 2015 — Soil organic matter, long thought to be a semi-permanent storehouse for ancient carbon, may be much more vulnerable to climate change than previously thought. Scientists have found that the common ... full story

Mar. 31, 2015 — Using the assessment tool ForWarn, US Forest Service researchers can monitor the growth and development of vegetation that signals winter's end and the awakening of a new growing season. Now these ... full story

Mar. 31, 2015 — Until now electric fences and trenches have proved to be the most effective way of protecting farms and villages from night time raids by hungry elephants. But researchers think they may have come up ... full story

Mar. 31, 2015 — The endangered desert pupfish has made itself at home in the harsh, hot environment of Death Valley hot springs by using a surprising evolutionary adaptation: They can go for up to five hours without ... full story

Mar. 31, 2015 — Researchers have detected a human fingerprint deep in the Borneo rainforest in Southeast Asia. Cold winds blowing from the north carry industrial pollutants from East Asia to the equator, with ... full story

Mar. 31, 2015 — A team of engineers and biologists reports new progress in using computer modeling and 3D shape analysis to understand how the unique grasping tails of seahorses evolved. These prehensile tails ... full story

Mar. 31, 2015 — As the five-year anniversary of the explosion of the Deepwater Horizon oil rig approaches, a new report looks at how twenty species of wildlife are faring in the aftermath of the ... full story

Mar. 31, 2015 — Scientists have uncovered the earliest fossilized evidence of an insect caring for its young. The findings push back the earliest direct evidence of insect brood care by more than 50 million years, ... full story

Giant Amphibian Fossils Found in Portugal

Reuters - Light News Video Online (Mar. 31, 2015) — Scientists discover a new species of giant amphibian that was one of the largest predators on earth about 220 million year ago. Tara Cleary reports.
Video provided by Reuters

Bionic Ants Could Be Tomorrow's Factory Workers

Reuters - Innovations Video Online (Mar. 30, 2015) — Industrious 3D printed bionic ants working together could toil in the factories of the future, says German technology company Festo. The robotic insects cooperate and coordinate their actions and movements to achieve a common aim. Amy Pollock reports.
Video provided by Reuters

Related Stories

Mar. 7, 2014 — A new study found more than 80 percent of raw chicken used in hospitals in food for patients and staff was contaminated with a form of antibiotic resistant bacteria called extended-spectrum ... full story

Jan. 29, 2014 — The regular appearance of food poisoning in the news, including a recent event that led to the recall of more than 33,000 pounds of chicken, drives home the need for better bacterial detection long ... full story

Jan. 11, 2012 — A short burst of low voltage alternating current can effectively eradicate E. coli bacteria growing on the surface of even heavily contaminated beef, according to a new study. The technique offers an ... full story

Aug. 15, 2011 — Sanitizing the outside of produce may not be enough to remove harmful food pathogens, according to a new study that demonstrated that Salmonella and E. coli can live inside plant ... full story

Aug. 4, 2011 — Researchers have discovered and received a patent for a naturally occurring lantibiotic -- a peptide produced by a harmless bacteria -- that could be added to food to kill harmful bacteria like ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.